Fuel tanks for automotive and similar applications are conventionally constructed of a polyethylene-based material composition. Materials of this composition possess a number of properties that are detrimental to forming a connection between the fuel tank and the fill pipe. Specifically, polyethylene-based materials tend to absorb fuel and to creep under load. The absorption of fuel causes the material to swell and change geometry. Creep, which is accelerated by absorption of fuel, allows the polyethylene material to change geometric form under constant or changing load. These two factors, which can alter the dimensional characteristics of the material, are not predictable in amount A connection between the fuel tank and the fill pipe must be predictable and of controllable geometry to ensure that sealing retention force is sufficient for proper function of the connection.
Moreover, once the fuel fill pipe and tank have been installed in the vehicle and are operable in use, there is still a need to prevent spit or well back after the refueling operation has stopped. There also remains a need to prevent fuel from leaving the fuel tank in the event that the fuel tank connection is compromised or the fill pipe develops a leak path. Hitherto various tank filling constructions of the prior art have incorporated some type of check valve to prevent such back flow of fuel from the tank into the filter pipe. Older versions of such check valves sometimes used a floating ball mechanism, but such a design is incapable of forming a leak-tight seal and is generally being phased out. More modem check valves provided for this purpose work by spring action holding an elastomeric seal type between the opposite sealing surfaces of the check valve construction.